Treatment of hydrocarbon oils



Patented Apr. 17, 1934 warren stares FFE E TREATMENT or nvnnooannon OILSNo Drawing. Application June 6, 1931,

Serial N0. 542,703 w i.

Claims.

This invention relates to the treatment of hydrocarbon oils and refersmore particularly to the treatment of the lower boiling distillatesproduced in the cracking of the heavier portions of crude petroleumsthough corresponding distillates resulting from straight run distillations may also be treated.

ing oper- More specifically the invention has reference to the treatmentof distillates containing able amounts of gum and color-form undesiringcompounds and sulphur in higher percentage than is allowable incommercial motor fuels by new and novel means particularly adapted toeconomically refine the distillates to produce marketa fuel therefrom.

ble motor In one specific embodiment the invention comprises treatinghydrocarbon distillates, particularly cracked hydrocarbon distillatescontaining substantial amounts of gasoline boiling range, with the saltsof persulphuric acid which are known as persulphates.

The steps most commonly used to reduce the gum and sulphur content andimprove stability of cracked. distillates may be in general outlined asfollows:

the color 1. Treatment with caustic soda to remove dissolved hydrogensulphide;

2. Treatment with sulphuric acid of cial grade;

3. Neutralizing with caustic soda;

4. Treatment with plumbite or other common sweetening reagents toconvert meroaptans to odorless and relatively non-corrosive disulphides;

5. Redistillation to produce an overhead gasoline of proper end point;

6. Final neutralization or sweetening.

While the use of sulphuric acid is quite universal, it possesses adisadvantage in its lack of selectivity in removing undersirabie diandtriolefins while leaving substantially unaffected the monoolefins whichadd to the antiknock value of the gasoline so that when sufiicient acidis used to remove the undesirable highly unsaturated hydrocarbons aportion of the less high 1y unseturated are removed concurently.Furthermore, if the temperature is allowed to rise to any extent or acidof high strength such as fuming acid conpresent invention is concernedwith t ments constituting an improvement ove he treatr the sulphuricacid treatment in that the reactions produced by the reagents used aremore selective and may be stopped short of excessive polymerization withresulting increase in yield of finished product. Further advantages willappear hereinafter. r

The persulphates are salts of the hypothetical persulphuric acid H2S2Oz.The most easily i'ormedpersulphate is that of ammonium which isconveniently prepared by the electrolysis of ammonium which isconveniently prepared by the electrolysis of ammonium sulphate incompartment cells, the ammonium persulphate being continuously formed byanodic oxidation, the anode solution being continuously replenished bythe addition of ammonium sulphate. This compound is a white crystallinesolid which has a specific gravity of 1.982, decomposes under itsmelting point and is soluble in water to the extent of 58.2 parts at 0C. and about 65 parts at room temperature in 190 parts of Water. Thesolutions when inoderatelyheated give off active or ozonized oxygenwhich assists in the treating eliects as will be hereinafter more fullydescribed.

Other persulphates such as, for example, those so of sodium or potassiummay be prepared by adding their carbonates or hydrates to concentratedsolutions of ammonium sulphate whereupon the persulphates of the alkalimetals precipitate. These compounds are somewhat less 5 soluble in waterbut may be employed advantageously in particular cases either alone orin combination with the ammonium salt. Persulphates of the followingmetals are also available: Lithium, caesium, rubidium, calcium,magnesium, strontium, barium, mercury, copper, silver, zinc, cadmium,thallium, lead, manganese, iron and nickel. Obviously the use ofparticular salts will be governed by the cost as Well as by their par?ticular chemical characteristics.

It is characteristic of the present invention that the persulphates maybe used either in aqueous solution or as finely divided solids. Whensolutions are used practical operations may be conducted generally inthe same manner and in the 165 same types or" equipment used withsulphuric acid. For example, treatments may be conducted atapproximately atmospheric temperatures by circulating the solution ofpersulphate from the bottom cone or" a batch agitator commonly used inoil refineries back into the top thereof through sprays or otherdistributing means, the circulation being continued until the solutionis spent and the' desired treating efieot has been produced. Similarlythe persulphate solutions persulphates upon hydrocarbon distillates inmay be used in lieu of sulphuric acid in continuous treating plants ofthe alternate mixer and settler type, the solution being injected intothe suction side of centrifugal pumps and being subjected to mixing withthe oils during passage therethrough and through lines containingbaffiing material. 1

Treatments may also be conducted by agitating oils with solidpersulphates, either by chemical stirring devices or by blowing withair, the amounts used depending upon the particular salt employed, thecharacteristics of'the oil to be treated and the degree of refinementdesired. It is to be noted here that owing to the fact that the basicityof the persulphates may be regulated by employing salts of difierentmetals, a wide variety of treating efiects is possible. Furthermore,oxidation effects appear to be produced by small amounts of ozone oractive oxygenrather than by oxygen in combination with sulphur as in thecase of sulphuric acid so that there is in general a reduced tendencytoward the 'formation of sulfoxy compounds which are both diffi'culttoremove from the oil when they remain dissolved therein and are dimcultto decompose to regeneratethe acid when present in the sludge resultingfrom acid treatments.

Temperatures employed, while conducting treatments, may be varied over awide range from temperatures substantially sub-atmospheric in theneighborhood of'20" F. to elevated temperatures as high as 200 F. orhigher, this condition being adjusted to suit the needs of theparticular stock under treatment and being determined in a large measureby the type of persulphate employed and the degree of refining effectdesired.

Pressures may also be varied though atmospheric or slightlysuper-atmospheric pressures are preferred.

' The chemical eifects produced by the use of place of sulphuric acidare in general of the same nature though the extent of polymerization,oxidation and miscellaneous side reactions resulting in the formation ofsulfoxycompounds may be better controlled. As an example of treatingresults obtainable by the use of persulphates as treating agents, acracked distillate produced from heavy California residuum may betreated with a saturated solution of ammonium persulphate at the rate ofapproximately six pounds ofisolid salt per barrel of oil. At this pointit may be noted that ammonium persulphate has a molecular weight of 228and contains approximately 35% sulphur trioxide by weight whilesulphuric acid, considered as monohydrate, contains 81.6% sulphurtrioxide. From this it will be seen that while an amount of persulphateis used corresponding in weight to the usual sulphuric acid treatment ofapproximately six pounds per barrel commonly practiced upon Californiacracked distillates, that the acid equivalent employed is substantiallyless.

The results obtained by using ammonium persulphate in the amountmentioned and redistilling to produce gasoline may produce a producthaving the following properties:

Gravity 55.4 A. P. 1. Color +30 Saybolt Sulphur 0.1%

Gums 25 mgs.

The persulphates may be used alone or in combination with other treatingreagents and as sulphuric acid, plumbite solution, solution of coppersalts, adsorbent earths, neutralization agents. Mixed solutions ofpersulphates and sulphuric acid are particularly eifective. Solutions ofpersulphates may be used effectively in the treatment of end pointcracked distillates requiringno redistillation. Preferably suchtreatment is followed by treatment with adsorbent earths. It will beevident from the foregoing disclosure and example that by the use of theprocess of the present invention cracke'd'hydrocarbon distillates' maybe efiiciently treated to produce finished gasoline conforming tocommercial requirements. The scope of the invention is not, nowever, tobe limited to the specific-descriptive material and example given sinceit"is aimed to cover broadly the use of persulphates in the treatment ofhydrocarbon oils either as a single treatment or a step in combinationwith other treatments.

I claim as my invention:

1. A process for refining hydrocarbon distillate which comprises,subjecting said distillate

